Natural and synthetic rubbery cellular products have many applications. One significant use for such products is the application of a layer of foam to carpet backing to provide an integral cushion. Synthetic latex foam is now used widely in the textile industry.
It is customary in compounding latex dispersions to add all the compounding ingredients except the activator prior to the foaming step. A commonly used activator is zinc oxide. However, if this procedure is followed, the zinc oxide present would induce premature coagulation during the foaming step. Therefore, zinc oxide is frequently added prior to the foaming step.
U.S. Pat. No. 3,969,289 discloses a one-part storable foamable latex composition. The composition comprises a natural or synthetic elastomeric latex that is subject to cure. A curing system is provided comprising an ammonia-retarded dibenzyl dithiocarbamate accelerating agent that is inhibited in accelerating function in the presence of a base, such as ammonia. The composition includes an amount of ammonia sufficient to inhibit the cure of the latex and a foaming agent. Most importantly, the composition includes a siloxane heat-sensitizing agent to lower the coagulation temperature of the latex to about 90 degrees F., or above. The latex composition disclosed in the '289 patent is disadvantageous because it requires the use of a specific heat sensitizing agent.
Thus, a one-part foamable latex composition that is stable against gellation for extended periods of time prior to or after foaming has long been sought in the art.